by Chris Peterson » Fri Sep 23, 2022 10:09 pm
johnnydeep wrote: ↑Fri Sep 23, 2022 9:50 pm
Ann wrote: ↑Fri Sep 23, 2022 5:02 am
Chris Peterson wrote: ↑Fri Sep 23, 2022 4:19 am
I would not describe Neptune's appearance here as "dark", and indeed, it has diffraction spikes about the same length as those of Triton.. because it is so bright.
Neptune diffraction spikes NIRCAM annotated.png
Indeed. Neptune's diffraction spikes are there, but they are much less obvious than the spikes of Triton, because they are broad and diffuse.
Ann
It looks like the diffraction spikes on Neptune could be due more to the bright rim than to the darker methane-induced IR-absorbing body. No?
There are many confusing things about the image. The spikes appear almost entirely in the blue channel, but that represents the shortest wavelengths, in the near-IR, where Neptune is supposed to be not very bright. Yet we see a bright white rim that suggests large amounts of near-IR as well as thermal-IR.
As always, trying to understand what's really going on is difficult or impossible using a color image like this. We really need to go back to the individual channels that the color image is constructed from. (In this case there are four source channels mapped onto three output channels, which represents an irreversible convolution of the data.)
[quote=johnnydeep post_id=326055 time=1663969852 user_id=132061]
[quote=Ann post_id=326036 time=1663909327 user_id=129702]
[quote="Chris Peterson" post_id=326035 time=1663906762 user_id=117706]
I would not describe Neptune's appearance here as "dark", and indeed, it has diffraction spikes about the same length as those of Triton.. because it is so bright.
[/quote]
Neptune diffraction spikes NIRCAM annotated.png
Indeed. Neptune's diffraction spikes are there, but they are much less obvious than the spikes of Triton, because they are broad and diffuse.
Ann
[/quote]
It looks like the diffraction spikes on Neptune could be due more to the bright rim than to the darker methane-induced IR-absorbing body. No?
[/quote]
There are many confusing things about the image. The spikes appear almost entirely in the blue channel, but that represents the shortest wavelengths, in the near-IR, where Neptune is supposed to be not very bright. Yet we see a bright white rim that suggests large amounts of near-IR as well as thermal-IR.
As always, trying to understand what's really going on is difficult or impossible using a color image like this. We really need to go back to the individual channels that the color image is constructed from. (In this case there are four source channels mapped onto three output channels, which represents an irreversible convolution of the data.)